Process of producing carbides and making acetylene therefrom



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R. G. WULFF PROCESS OF PRODUCING ABIDES AND MAKING ACETYLENE THEREFROMFiled och 14, 1929 M/ J n /ln m/ m @w w t om( f a ww n.

4v-TO @NEM Patented Apr. 2, 193-1' PATENT :OFFICE I PROCESS F PBODUCINGCARBIDES AND MAKING ACETYLENE THEBEFBOM Robert G. Wulff, Los Angeles,Calif., assigner to Wulff Process Company, Los corporation of CaliforniaAngeles, Calif., a

Application October 14, 1929, No. 399,516

llClaims.

'I'he present invention concerns a process of making alkalioralkali-earth metal carbides and for producing acetylene therefrom. Theprocess has for its object the manufacture of such carbides andacetylene continuously and without the aid of electric heat, althoughthe latter may be used `if suiiciently cheap. A further object of theinvention is to expedite carbide formation and acetylene formation bycontinuous removal l0 of carbon monoxide from the sphere of therevaction, which it has been determined exerts a retarding eiect uponthe desired reactions if allowed to remain.

In my study of the ordinary process of making calcium carbide, I came tothe conclusion that the reason for the high temperature required wasthat the reaction was so conducted as todemand that temperature for thereduction of lime rather than for the formation of carbide. vA furtherconclusion wasthat alkali forming metals and alkali-earth metals otherthan calcium were more suitable for the easy formation of carbides atcomparatively low temperatures.

In the process which has been worked out and v whichis susceptible ofnumerous modications, the result aimed at has not been the production ofa high grade of carbide, but rather the efiicient production ofacetylene from superiicially carbide-coated or carbide-impregnated metaloxides or carriers therefor.

- Briefly stated, my process comprises circulatingrather coarsefragments of alkali or alkaline earth oxide or hydroxide or cokeimpregnated with such oxide or hydroxide through a vertical gas-redfurnace through which hydrocarbon or hydrogen gas or a mixture of theseis blown in counter-current to furnish carbon, if

been invented with the particular objects of be-y ing able to producean-uncontaminated product quickly, continuously, safely, andefficiently.

In the drawing I0 indicates a housing in which runs a belt conveyor IIupon which the oxide material I2 to be treated is returnedfrom previoususe to a furnace supply magazine I3.

Above the magazine is superposed-a new mate- .rial feed chamber Il fromwhich a supply of oxide may be added through conical valve Il to thesupply of oxide .already in the system. A manhole I6 in the top ofchamber I4 admits of 5 filling the latter chamber. 'I'he shell Il whichencloses chamber ormagazine I3 also encloses two other chambers I8 andI8 located in the order named below chamber I3. The floors of chambersI3 and I8 are each provided with a l0 conical valve v20 and 2Irespectively. Both chambers I8 and I9 have entering them respectiveexhaust pipes 22 and 23. A vacuum pump or exhauster and gasometer (notshown) is connected to pipe 22. I l

Below chamber I9 there is a vertical refractory tube 26 which may bemade of carborun-l dum, sillimanite, or porcelain. The carborundum orlike tube encloses an inner one 28 which is made of graphite. Both.tubes are cemented or 2o otherwise fastened into shell Il in agas-tight manner and both are encircled by a refractory furnace wall 29about their middle section.

The wall 2l is of special construction; it encloses a comparativelylarge heating space 30 into which 25 two or more burners 2| project.'I'he burners are supplied with air and fuel through an annular manifold22 which in lturn may be supplied with airfrom pipe 22 and fuel frompipe 24. The purpose of the two pipes is to make the preheating 30 ofair possible since pipe 23 connects with thel manifold I2 througha'preheating coil 35 which encircles the furnace tubes 2l and 2l andwhich is heated by combustion products escaping through flue vents 38.An annular void 31 may 3 5 be provided to lighten the weight of thefurnace Wall.

Below the furnace there is another metallic shell 38 very similar toshell Il except that it occupies a vertically reversed position. `Thecarbo- 40 rundum and graphite tubes are fitted into shell 38 in the samemanner as into shell I1. Immediately below the point 39 at which suchfitting occurs, there is a chamber 4l, in the bottom of which isaIconical valve II.

Below chamber 40 is a chamber 42 containing in its floor the conicalvalve l2. Entering chambers III and 42 from the side and near the topsthereof are pipes M and I5 respectively. Pipe 44 delivers methane,artificial or natural gas, or hydrogen to 50 the apparatuswhile pipe 45is connected to a vacuum pump through thevalve III for causing a vacuumin chamber 42.

A third chamber 41 is situated in the shell 2l below chamber I2: itsiioor is conical and has a valve- 56 less opening 48 through whichoxide-carbide material may be dropped upon a traveling belt 4S which isenclosed in a housing 58. From the top of the housing there extend4vertically upward pipes 5| and 52. Pipes 52, into which is connected ablower 53, is arranged to deliver gas derived from the interior ofhousing 50 into pipe 5|. Gas from pipe 5I traverses a chamber 54,however, before being delivered into pipe 52. 'Ihe chamber 54 is ahumidifying box containing water 55 in which there is submerged anelectric heater 56 connected through a suitable rheostat 51 to a sourceof electrical energy 58. A pipe 59, in which there is a valve 60, isarranged to deliver water to the bottom of the box. Pipe 5I, the purposeof which is to dispose of excess acetylene generated within thehousings, is connected with a storage gasometer (not shown) for thefinished.

acetylene.

Belt 49 passes over left and right pulleys 6I and 62 respectively. Belowpulley 62 is an inclined screen 63, the meshes of which are of a sizethat will retain particles of the size chosen for the oxide, but whichwill pass particles which have had their size materially reduced throughwear or disintegration. The screen is arranged to be vibrated by theaction of a cam 64 which is revolved rapidly by any suitable means.Below the screen is a reservoir space 65, at the bottom of which is adischarge hopper 86.

The point of discharge of the retained material from screen 63 is soarranged that the coarse material falls into a pocket 61 of a housing 68which encloses a vertically arranged bucket type conveyor 69. The latteris arranged to discharge lifted oxide onto belt I I, previouslymentioned. All operations are conducted within housings of a gas-tightnature.

When using the above described apparatus to carry out my process, thesequence of operations occurs as follows:

All valves shown are closed, and manhole I6 opened to charge oxide orhydrated oxide particles or coke particles impregnated with suchmaterial. Particles in any event are of about one-half inch size. ValvesI5, 29, and 2| are opened to permit all this material to fill thechamber 40, the tube 28,'and the chambers I9, I8, I3, and I4. Manhole IBis then tightly covered again. Fuel is turned on through the pipe 34 andair through the valve 12, the mixture being lighted in the fire-box 3B.At the same time iiushing gas is turned on through the valve 13, whichenters the chamber 40, passes up through the charge in the tube 28,enters the chamber I9, and makes exit through the pipe 23 to a receiver,not shown. This gas is hydrogen if no carbon is necessary to the chargebeing treated other than said charge already contains, as for instancewhen impregnated coke is used. The gas may contain hydrocarbons such asthe lighter paraflin hydrocarbons, if additional carbon is needed. Itmay even be pure methane, and the speed of its passage adjusted to thetemperature therein so that only the proportion desired has time todecompose and form carbon for the reaction of forming carbide. Forpurposes of flexibility there may be added to this methane' a minorproportion of higher paraiilns, preferably ethane.

As soon as sufficient time has been allowed for the furnace and itscharge to reach an operating temperature, chamber 42 is evacuatedthrough the valve 10, which is then shut again. Valve 4| is then openedto allow for the filling of the chamber 42 with treated material. At thesame time the void space in said chamber is lled withgas from thechamber 40. Valve 4| is again closed, and the gas in the void space ofchamber 42 withdrawn by evacuation as before. Valve 43 is then opened tolet chamber 41 be filled from chamber 42. This now admits gas fromchamber 4l to chamber 42, which must be withdrawn before chamber 42 isagain lled with a charge.

Each time material is dropped from chamber 40 into chamber 42, theheated charge in the tube 28, being loose slides down accordingly, andchamber I9 in this way is substantially emptied. Thus each time thechamber I9 is emptied there must be a refilling sequence of operationson the connected chambers I8 and I3. Chamber I8 is rst evacuated throughvalve '|I, and said valve again closed. Valve 2| is then 'opened andchamber I8 emptied into chamber I9. With this operation gas lls the voidspace in chamber I8 from the chamber I9. This gas is evacuated from thechamber I8 as before, after closing valve 2|. Chamber I8 may then againbe filled by opening valve 20. This operation admits gas from chamber I3into the chamber I8, which gas is again evacuated after closing valve20.

The rate of passage of material through the tube 28 will be dependent onthe design of the furnace used, the nature of the charge used, and thetemperature employed. It is safe to say, however, that the desirablething is the formation of a superficial coating of carbide-impregnatedparticles, of from 1`/64th to l/th inch in thickness. The movement ofparticles or charge through the furnace is seen to be intermittent, butthe size of the chambers feeding and withdrawing material is made smallenough to be continuous, for practical purposes. visable to have theproportion of chambers below the tube 28 such that chamber 4`| is neverentirely empty, but is continually feeding material onto the conveyorbelt 49. These chambers must also be properly proportioned to thechambers above tube 28 so that the tube 28 is at all times full ofmaterial for treatment.

The purpose of the multiplicity of chambers II and 38 is to provideagainst contamination of the acetylene generated by the flushing gas.Chambers 4`| and I3 are at all times full of pure acetylene, and whencommunication from these chambers to the chambers 42 and I8 respectivelyis made, said latter chambers must first be evacuated.

One of the particular advantages of my process resides in the fact thatthe upward sweepingcurrent of methane, etc., carries away and dilutesthe carbon monoxide formed in furnace tube 28 and thereby acts to removea hindrance to the progress of the carbide-forming reaction. Thecontaminated flushing gas may be freed from carbon monoxide by anysuitable known means and used over again in the process, although Iprefer to convert the CO into methane and water in the known manner byadding the quantitatively necessary amount of hydrogen and then passingthe mixture over a heated nickel catalyst. The gas is then preferablydried before reuse.

. Carbide-coated granules which have passed chamber 42 automaticallydrop onto belt 49 and are there exposed to the damp atmosphere generatedby humidifying box 54, in which the water is kept vaporizing throughbeing continuously electrically heated. Evolution of acetylene from thecarbide coating takes place, filling housings 50, 68, and I 0 withacetylene, which is continuously circulated through box 54 by blower 53in a left to right direction. This movement will bring It is alsoadvolumes of wet gas into counter-current contact with thecarbide-coated particles on belt 49, which will result in the drying ofthe acetylene and the generation of more acetylene. In time such anexcess of acetylene will be generated that it will be forced to seek itsexit through pipe 5| to the acetylene storage gasometer, not shown.

The vibrating screen 63 operates to separate all fines from the oxideparticles and to dump the denuded large granules of oxide into conveyorpocket 61. Such ilnes as drop through the screen may be collected fromhopper 66, and calcined to convert all hydroxide into oxide and then bere-granulated and recharged into the apparatus. 'Ihe granules reachingpocket 61 are lifted by conveyor 69 and dumped upon belt il, which againdrops them into chamber I3.

While the above matter suiliciently describes the mechanical and thermalarrangements, some additional remarks upon chemical considerations mayaid in understanding the breadth of those aspects of the invention.

Barium oxide is the preferred basic oxide, but strontium, sodium, andcalcium oxides may also be used, and these-may at times be in thehydrated state, as for instance after leavingthe acetylene-generatingchamber 50.

-The oxide chosen may be pelleted to suitable size with a carbonizingbinder such as dry pitch or molasses. As an alternative, coke may bebrought to the proper mesh, and impregnated at high temperature with themolten basic oxide or hydroxide used. It may be seen also that from thesimilarity of the different basic materials mentioned, they may be usedin admixture to get desired intermediate properties such as modifledalkalinity. 'I'he description of such materials as a metal compoundselected from the group comprising the alkali forming metal'oxides andhydroxides and the alkali earth metal oxides and hydroxides means,therefore, one of such coml pounds alone, or a mixture of any two ormore of such compounds. Likewise, the description of such materials asan oxide 4or hydroxide selected from such group means any oxide orhydroxide from such group, alone, and any oxide or hydroxide from suchgroup together with any one or more ofthe oxides or hydroxides'from suchgroup.

It is to be observed that where bonded oxide material is fed into thefurnace, there will be carbon added supercially. to the charge in thehottest portion of the furnace by the addition of methane or other cheaphydrocarbon to the flushing gas. Flexibility is at hand in the choicebetween methane and ethane, which show great difference in the ease withwhichv they decompose under heat to yield carbon. The ratio of these canbe` adjusted, so that with suitable rate of flow of flushing gas, therewill be just enough carbon liberated on the surface of the charge. Thedescription of the employment of a suitable hydrocarbon in the process,therefore, means the employment of methane, ethane or other suitablehydrocarbon alone or in any combination with each other. In any case theflushing gas has the function of removing carbon monoxide, by-product ofthe carbide-forming reaction which otherwise retards carbide formation.

`The source of flushing gas is immaterial, as long as'it does notcontain carbon monoxide in yappreciable amounts. Such flushing gas maybe made from oil by a separate furnace in which the same may be cracked.This will furnish a mixture ot hydrogen and varying amounts of'gasolines may be removed by known means.

These heavier constituents are not desirable in large quantities in theushing gas because they decompose too easily under heat.

Flushing gas making exit from the furnace can be used to any extentrequired for fuel in the burners 3|, and if there is any excess, it maybe treated by any known means to remove the carbon monoxide so as tomake it usable for flushing gas again.

Depending upon the metal oxide or hydroxide used, the maximumtemperature attained by the charge, which is the carbide formation zone,will vary from anywhere between 900 to 2800" F., being lowest for sodiumoxide and highest for calciurn oxide. Barium oxide will require atemperature of from 1400 to 1800 F.

In the formation of carbides by this process a temperature for theparticular metal oxide has to be reached where said oxide willmaterially reduce to metal and carbon monoxide. At the same time thetemperature must not be highy enough to prevent formation of carbidefrom the metal and carbon, or to decompose any such carbide formed.

Chemical considerations also enable the lshowing of my essential processin a modified form which is, however. not recognizable mechanically ashaving much relationship with the process just described. The modifiedlmethod is to melt NaOH or KOH in a deep iron crucible and then tobubble methane orl natural gas therethrough. If finely divided carbonwere suspended in the melt, hydrogen may be the gas bubbled through. Inany case there will occur carbide formation under conditions favoringthe continuous removal of CO by a flushing gas (methane and liberatedhydrogen). I'his form of my invention avoids the feature in the formfirst described of forming carbide through a progressively thicker andthicker shell of already formed carbide. The action of removing carbonmonoxide from under this shell becomes more diiilcult as the shell getsthicker. In the case of the second form, we are working with a liquidmaterial in which the carbon monoxidewill always be easily removed, suffering dilution immediately upon forming. This effect, however, can besecuredv with the impregnated coke, if said coke in the tube 28 is heldat a sufliciently high temperature for the basic oxide to be in a moltencondition, held in place by capillarity.

I claim as my invention: l. A cyclical process of forming acetylenewhich consists in: contacting particles of an oxide or hydroxideselected from the group comprising the alkali-earth metal oxides and thealkali-forming metal oxides and' hydroxides with a gas rich in methaneat carbide-forming temperatures, said temperatures being obtained byburning a combustible mixture, contacting the carbidebearing particleswith a moist atmosphere, thereby obtaining acetylene andthe originalparticles, and `recycling said original particles.

2. A cyclical Vprocess of forming acetylene which consists in:countercurrently contacting particles of an oxide or hydroxide selectedfrom thel group comprising the alkali-earthA metal oxides and thealkali-forming metal oxides and hydroxides with a gas rich in methane atcarbide-forming temperatures, said temperatures being obtained byburning a combustible mixture,

moist atmosphere, thereby obtaining acetylene and the originalparticles, and recycling said original particles.'

3. A cyclical process of forming acetylene which consists in: contactingparticles of an oxide or hydroxide selected from the group comprisingthe alkali-earth metal oxidesv and 'the alkaliforming metal oxides andhydroxides with a gas rich in methane at carbide-forming temperatures,said temperatures being obtained by burning a combustible mixture, saidgas being supplied under such conditions as to continuously removecarbon monoxide at substantially the same rate at which it is formed,contacting the carbide-bearing particles with a moist atmosphere,thereby obtaining acetylene and the original particles, and recyclingsaid original particles.

4. A cyclical process of forming acetylene which consists in: contactingparticles having a surface of a metal compound selected from the groupcomprising the alkali-earth metal oxides and the alkali-forming metaloxides and hydroxides with a gas rich in methane at carbideformingtemperatures, said temperatures being obtained by burning a combustiblemixture, contacting the carbide-bearing particles with a moistatmosphere, thereby obtaining acetylene and the original particles, andrecycling said original particles.

5. A cyclical process of forming acetylene which consists in: contactingparticles of coke impregnated with a metal compound selected from thegroup comprising the alkali-earth metal oxides and the alkali-formingmetal oxides and hydroxides with a hydrogen containing gas atcarbideforming temperatures, contacting the carbidebearing particleswith a moist atmosphere, thereby obtaining acetylene and the originalparticles, and recycling said original particles.

6. A cyclical process of forming acetylene which consists in: contactingparticles of coke impregnated with a metal compound selected from thegroup comprising the alkali-earth metal oxides and the alkali-formingmetal oxides and hydroxides with a hydrogen containing gas atcarbideforming temperatures, said gas being supplied under suchconditions as to continuously remove carbon monoxide at substantiallythe same rate at which it is formed, contacting the carbidebearingparticleswith a moist atmosphere, thereby obtaining acetylene and theoriginal particles, and recycling said original particles.

7. A process of producing acetylene which consists in: countercurrentlycontacting particles of one or more metal compounds selected from thegroup comprising the alkali-forming metal oxides and hydroxides and thealkali-earth metal oxides and hydroxides with one or more suitablehydrocarbons at carbide-forming temperatures so that the hydrocarbonreacts with the particles to form carbide; treating the particles toform acetylene from said carbide; and utilizing the particles after theacetylene has been so produced in the formation of additional carbide.

8. A process of producing acetylene which cornprises: forming a carbideby subjecting a suitable hydrocarbon to the action of heat in thepresence of particles of a metal compound selected from the groupcomprising the alkali-forming metal oxides and hydroxides and thealkali-earth metal oxides and hydroxides so that the hydrocarbon reactswith the outer surface of the particles to form a carbide; treating theparticles to form acetylene from said carbide; and utilizing theparticles after the acetylene has been so produced in the formation ofadditional carbide.

9. A process of producing acetylene which comprises: heating ahydrocarbon to a temperature in excess of l400 F. in the presence ofparticles of a metal compound selected from the group comprising thealkali-forming metal oxides and hydroxides' and the alkali-earth metaloxides and hydroxides so that the hydrocarbon reacts with the outersurface of the particles to form a carbide; treating the particles toform acetylene from said carbide; and utilizing the particles after theacetylene has been so produced in the formation of additional carbide.

10. A process of producing acetylene which comprises: subjecting asuitable hydrocarbon to the action of heat in the presence of particlesof a metal compound selected from the group comprising thealkali-forming metal oxides and hydroxides and the alkali-earth metaloxides and hydroxides so that the hydrocarbon reacts with the outersurface of the particles to form a carbide, the hydrocarbon being passedthrough the reaction zone ln gaseous form in sufficient quantities torapidly remove from that zone any carbon monoxide formed therein;treating the particles to form acetylene from said carbide; andutilizing the particles after the acetylene has been so produced in theformation of additional carbide.

11. A process of producing acetylene which comprises: forming acetyleneby heating a hydrocarbon to a temperature in excess of 1400 F. in thepresence of particles of a metal compound selected from the groupcomprising the alkaliforming metal oxides and hydroxides and thealkaliearth metal oxides and hydroxides so that the hydrocarbon reactswith the outer surface of the particles to form a carbide, thehydrocarbon being passed through the reaction zone in gaseous form insuiiicient quantities to rapidly remove from that zone any carbonmonoxide formed therein; treating the particles to form acetylene fromsaid carbide; and utilizing the particles after the acetylene has beenso produced in the formation of additional carbide.

ROBERT G. WULFF.

